1. Field of Invention
This invention relates to a mouth moistener to relieve the symptoms of dry mouth condition and more particularly, to a mouth moistener which is storage stable and relieves dry mouth condition without damage to tooth enamel.
2. Prior Art
Dry mouth is a subjective clinical symptom characterized by a less than a normal amount of saliva with no apparent boundary between normal and abnormal. Dry mouth condition occurs in all age groups and is brought about by numerous reasons, including advancing age, drug, alcohol and nicotine abuse and as side effects in the use of many commonly used prescription medicines such as anti-depressants, antihypertensives and anti-histamines among others.
Various therapeutic measures have been recommended for patients experiencing dry mouth. Some of these include frequent rinsing with saline solutions to keep oral tissue moist and healthy. A second approach is the use of various agents to promote salivation. For example, U.S. Pat. No. 4,820,506 discloses an aqueous composition to stimulate salivation to relieve the symptoms of xerostomia wherein the composition is an acidic (pH 3-4) water solution having dissolved therein 2-3% of a food grade acidulent such as citric acid or malic acid. Because repeated use of acidic solutions is potentially harmful to human teeth and can cause demineralization of tooth enamel, the solution is saturated with calcium phosphate to inhibit damage to tooth enamel. It has now been determined that the inhibition of demineralization afforded by the presence of saturated calcium phosphate in solutions containing citric acid is only temporary, as the calcium phosphate is supersaturated with respect to a less soluble calcium citrate which forms in the solution during storage and precipitates therefrom. The precipitation of calcium citrate leaves the solution undersaturated with respect to calcium phosphate and the demineralization inhibition effect of the phosphate salt is as a consequence substantially diminished. Further, the presence of the calcium citrate precipitate in the solution renders the product aesthetically unappealing as well as causing malfunctioning and clogging of the spray pump systems used to apply the product to the oral cavity for relief of dry mouth condition. In addition, the acidic solution disclosed in U.S. Pat. No. 4,820,506 has been found to impart an unpleasant, pronounced sour or tart taste due to the presence of the relatively high concentration of organic acid making the product unsuitable for use as a mouth moistener.
Therefore, there is a need in the art for mouth moistener which is storage stable, has a less pronounced sour taste and with repeated use is without diminished effect for protecting the tooth enamel of the user.